[3.12] gh-107801: Improve the accuracy of os.lseek docs (#107935) (#108136)

- name the last parameter *whence*, like it is for seek() methods on
  file objects
- add param docstrings
- structure the valid *whence* params

(cherry picked from commit dd4442c8f597af1ec3eaf20f7ad89c4ac7e2dbc9)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>